The purpose of this study is to better understand how insulin affects protein metabolism in humans. The specific aims are to determine the effect of intraarterial infusion of insulin on fractional synthesis rate of myosin and mixed muscle proteins in normal subjects and Type I diabetic patients, determine dose-related effect of insulin on protein dynamics, and to determine the validity of using Apo B as a marker of AA-tRNA label in liver in the fasted state during insulin infusion with or without amino acid replacement. This protocol is closed to enrollment. The sample analysis in the Mass Spectrometry Core Laboratory continues.